The first paper from my Ph.D thesis came about as a pleasant surprise! In order to ask some specific questions about male solo song in white-browed sparrow weavers (Plocepasser mahali), I began an intensive programme of monitoring male song at dawn (the main time of day when males produce their solo song). I soon discovered that sometimes they had already begun to sing when I arrived at the field site. This was very strange and infuriating!
Then one day it hit me. I was sat in the pitch black, waiting for the dawn chorus to start. Why were the birds being so lazy? Yesterday they had already been singing for 10 minutes by now! But the previous dawn had been different - even before I arrived on the bird's territory, at exactly the same time, I could see my hands and feet! I could make out the line of hills on the horizon, and the wildebeest shifting their weight from leg to leg. It was a full moon that day. The following day the moon hadn't yet risen and I couldn't even see my own hand in front of my face!
So perhaps this mattered to the birds. Maybe they only want to start singing when there is enough light for them to see their surroundings - after all, singing when there is insufficient light to see a predator approaching or to navigate escape could be deadly - they are a sitting duck, announcing their location to the world! Or perhaps they just don't wake up until it's bright enough, so their first 'good morning' song to the neighbours is just delayed until their natural alarm clock wakes them. I was full of questions.
This initial observation was both good news and bad news: something interesting was going on and I wanted to understand it, but this meant I had to get up even EARLIER every day to ensure that I didn't miss a thing! The study confirmed that there was indeed an effect of moon phase and position relative to the horizon on male song output. You can read the paper here.
One of the greatest thrills of working in the Kalahari is the view of the sky at night. Because it is so dark, you can see constellations of stars brightly shining in the pitch black sky. So if white-browed sparrow weavers are sensitive to even small amounts of variation in ambient light, then how do our birds back home in the UK cope with all the light pollution? Is this messing up their schedules? Sure enough, there is now a burgeoning literature on the effects of artificial lighting on songbirds. Street lighting at night can even influence their breeding physiology.
behaviour and evolution